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That analysis isn't too clear. It sounds like some economics student got ahold of some numbers and a calculator, and this is what he spewed in a late night drunken bull session at the dorm, and no one called him on his bullshit.

It is probably true that the economic unviability of varous energy schemes generally points to the fact that they may use up more energy than they create. It is probably a good first-order attempt at evaluating the "carbon footprint" of a Prius, for example, to see if it saves enough gas to pay for the expensive technology in it, as expensive components usually cost more in terms of carbon released to make.

However, this guy takes it too far. He observes that it is possible to swap dollars and energy in both directions; he uses the $10 word "fungible" which seems to have the effect of short-circuiting much of his gray matter; and then he asserts that money-losing PV schemes are actually consuming energy. Does this "educated stupid" egghead believe that an interest bearing account violates the laws of thermodynamics ?

I think more carefully researched guesses are that PV panels started breaking even around 2000 or so, and they produce more energy over their lifetimes than they took up to produce, now. (This is ignoring the fact that PV panels produced with cheap hydroelectric power in the Northwest can act as sort of batteries to export that cheap power to sunny places.)

This is the best link I know of that analyzes the PV payback issue (in terms of energy, not dollars):

http://www.ecotopia.com/apollo2/pvpayback.htm

its easy to debunk this myth.

Let's just say, for the sake of argument, that it takes 100 units of energy to make a PV panel. Then according to this myth, the panel only ever produces, say, 90 units of energy. The manufacturer pays for the 100 units of energy + materials to make the PV, and then sells it to the consumer for a profit. The consumer who buys this product (at a price which already accounts for 100 units of energy) is able to save more money than was spent on the purchase with only 90 units of energy? This is clearly not possible.

Either, there is no monetary payback from PV panels, or the ER/EI is greater than 1. But both cannot be true simultaneously. And the data shows that ER/EI is, in fact, greater than 1.

Estimated times for energy payback, from various sources:
(pdf) "1 to 5 years
various sources for estimates, all 1 to 5 years
"in the worst case, 4 years"
"usually under 5"
"range from 1 to 4 years"

Sorry but this is simply not the case. Typical solar panels even in 1994 would have a production energy pay-back period of around 50 months.
http://www.ecotopia.com/apollo2/pvpayback.htm
More modern cells are even better, typical payback of a couple of years depending on location.

On the other had financially speaking you are talking about 25 years to recoup the cost of installation, which is why adoption has to be promoted by governments as very few people are prepared to think that far ahead!.

They only reference one study, published in "Home Power" magazine, written by two people who appear to work for solar panel manufacturers (I think its this one: http://www.ecotopia.com/apollo2/knapp/PVEPBTPaper. pdf)

Anyone got a better source? I admit my info's a bit out of date- I had a lecture a couple of years ago from one of materials science prof's and that's about it. Can't seem to find anything definative on google - seems to be a lot of debate about how you make the calculations. Chiefly that many pro solar studies ignore the fact that you need a bunch of big, deep cycle batteries (with a life time of only a couple of years) to make a practical solar system. Many of the anti-solar people tend to use older silicon refining energy figures though.

I haven't got a source at hand right now, but IIRC solar energy doesn't require any more land than conventional energy. Remember, even oil wells, coal mines, dams and nuclear power plants need some space.

You owe me two minutes of my life back

BZZZZZZZTTTTT! BULLSHIT ALERT! BULLSHIT ALERT! I've seen this claim made more than once on Slashdot. Unfortunately I've never seen one single shred of evidence to back it up. Do you have any sources for this? I can find at least one paper on Google that says that this is bullshit.

One source that I've been unable to locate again actually said that the PV cells use more energy to manufacture than they will produce over their lifetime.

As a starter, here's a page with a number of stats, but being from a site called "ecotopia" makes the engineer-cynic in me want to take it with a grain of salt. They are, however, citing other studies. The more facts, the merrier, so if you've got any links, post.

The short version is that amorphous (thin-film) panels yield a 400%-2000% payoff on energy investment. That range is worst-case to best-case lifetime for the panels. Thin-film is the way to go anyway, as it's around $15/sq. foot instead of the $60/sq. foot for the crystalline panels. Sure, crystalline is twice as efficient, but thin-film is cheap enough to use as siding on your house, and you'll make up the difference in area. Now, as to convincing your significant other that shiny purple-blue panels are the way to clad your house is the tough part.

Look at it this way-- based on the energy costs, even if the return was only 110%, it would be worth doing. Is there any other way to turn a barrel of oil into 1.1 barrels of oil?

Could you please back your statements up with some sort of facts, preferably from a reliable source?

This source seems to suggest otherwise. Btw, the mass-production of solar-cells has begun after the publishing of this paper.

>during their (short) usable lifetime
I don't know about your experience. But I've had a solar cell, which has been serving me well for longer than 20 years. Guarantees are usually issued for 20 years lifetime.

Interestingly, I've heard similar stories about nuclear plants. Not that I'm claiming that they are true.

Stop being so sarcastic and just call a rat a rat

I know this is a naughty, but I am really curious. Do you have any references on this? Do you mean that electric cars are more energy efficient (total energy cycle) than equivalent gasoline powered cars?

Here are some figures.

The NiMH model of the EV1 is rated to consume about 370 watt-hours AC per mile. The PbA version was more efficient, about 270 WhAC/mi. I've driven both models, and I've confirmed these figures. (The NiMH model is worse mainly because of GM's kludgey use of the air conditioner to cool the battery pack during charging. A good liquid-cooled design would be much more efficient.)

Gasoline is about 125,000 BTU/gallon, or about 36.6 kW-hr. So a car that gets 25 mpg consumes about 1464 watt-hours/mile, or about 4 times that of the EV1.

So if the efficiency of the power grid, from primary fuel to customer, is greater than about 25%, then the EV1 wins on overall energy efficiency. Large combined-cycle gas-fired turbines now yield efficiencies in excess of 50%, large alternators are practically 100%, and the grid efficiency in California is about 96%. So the EV1 wins.

It's even better than that, because I've ignored the energy used in the production of gasoline from crude oil. And the EV also has the qualitative advantage of being able to use electricity from any primary source, while the gasoline car can only run on petroleum (although it could be converted to run on compressed natural gas.)

As far as solar, again it depends on a lot of things. And, the cost per kw (if you ignore unreasonable subsidies, such as California and Arizona laws that force the power companies to buy your unreliable power back at your whim by running your meter backards) is much, much higher.

Even without subsidies, solar is within a factor of two. That may qualify as "much, much higher", but the long-term trend on solar prices is steadily down while the trend on fossil fuels is steadily up. Eventually, they'll cross. So it seems reasonable to get started now, and to use subsidies to help the economies of scale kick in.

My PV power is quite reliable -- whenever the sun shines, I get power. It has kept my house going several times when the utility failed (though I had to "spill" the excess generation.) Net metering is hardly "unreasonable" when you consider that the effect of my generation is to slightly lower the net consumption of my neighborhood. When net-metered photovoltaic becomes a significant fraction of grid capacity, then we can reconsider net metering. I'd be happy to have that problem.

I note that electricity demand is usually greatest exactly when the sun is shining, because of heavy air conditioner use. I take advantage of this fact by having a time-of-use meter; I generate most of my PV electricity during peak periods when it is most valuable, and I buy it back at night at lower rates.

My home, in the summer, runs about 15kW for about 18 hours a day!

I would also be interested in the 2 year energy cost payback on cells in the southwest. Not that I disbelieve you, but I would love a source.

I typed "photovoltaic payback" into Google and immediately got several pages of links with that information. It seems to be a popular topic of study. A particularly detailed analysis is here

Could you please send a note to Home Power magazine, then? I'm sure they'd like to update their statistics.

If they can't be bothered to do their own research - like, say, five minutes with Google to find this, or this, or this - why should I do it for them?

But then, the last link I give above says "...a recent, very detailed study about solar panel energy payback time in the January 2001 issue of Home Power magazine...finds payback time for a standard module to be about 3.3 years, and 1.8 years on a thin-film panel." So maybe they are doing their research and you're reading back issues from the 1970s?

Not true. It takes from one to several years to break even, depending on the technology, but the claim that they take more energy than they put out is pure FUD.

Also, if you're far enough away from the grid it can actually be cheaper to install a photovoltaic system than to run copper and get on the grid.

I understand your motivation, but are you aware that a solar cell takes more energy to manufacture than it will produce over its working life?

Also, if you're far enough away from the grid it can actually be cheaper to install a photovoltaic system than to run copper and get on the grid.

Tom Swiss | the infamous tms | http://www.infamous.net/

You've launched a rather incomplete assault on renewable energy sources here. Yes, large-scale hydro is no longer an option -- it causes too much harm to existing ecosystems, and there aren't many places left to put big dams anyway. And yes, wave- or tidal-power collectors or ocean thermal taps cannot produce large amounts of power without huge pieces of machinery. But you've skipped right over the renewable technologies that are actually being installed today -- wind and solar systems.

Wind: "Good wind areas, which cover 6% of the contiguous U.S. land area, have the potential to supply more than one and a half times the current electricity consumption of the United States." And the wind turbines being built today can capture this energy at about the same cost as operating a natural gas turbine or a coal plant, and less than half of the cost of nuclear power (wind has no fuel cost, so all of the cost of power comes from paying off the original investment in the equipment).

Solar: Enough sunlight strikes the U.S. to meet our electricity needs 700 times over. Solar cells are currently quite expensive to manufacture, so their power costs more than coal or gas. Unfortunately solar cells are now caught in a catch-22. They could become the cheapest power source in the world, but not until they are manufactured in really high volume, and that's not happening because they're so expensive. (We all know what happens when you start manufacturing silicon chips in high volume...) Although they're not there yet, prices are falling, and solar cells will become the preferred energy source eventually.

The great thing about photovoltaic cells is that they let us get our electricity from a huge fusion reactor that is conveniently located 100,000,000 miles from any population center.

P.S.: Solar cells have an energy payback time of 1-4 years, so they produce 8-30 times more electricity in their lifetime than they require to manufacture.